There have been known cameras, such as on-vehicle cameras and surveillance cameras, that are frequently exposed to an outdoor environment. A lens unit for such cameras for outdoor use is exposed to rainwater and cleaning fluid, letting water droplets sit on a surface of an optical member such as a lens. Since the water droplets on the surface of the optical member affect imaging performance of an optical system, it is desired that the water droplets be removed.
For the removal of the water droplets, it has been suggested to remove droplets of the cleaning fluid injected at the lens of the on-vehicle camera by utilizing a capillary phenomenon of a groove provided under a sensor cover (see PLT 1).